Intro to Millwright Practice Exam 2026 – Comprehensive All-In-One Guide for Exam Success!

When using an inside micrometer, the component that must be turned constantly is the thimble. The thimble is designed to facilitate precise adjustments to the measurement. As the millwright turns the thimble, it moves the measuring rod either in or out, allowing for accurate and consistent readings of the internal dimensions of a workpiece.

The thimble typically has a graduated scale that provides precise measurement increments, and turning it adjusts the micrometer’s internal measurement capacity. This adjustment is crucial for achieving exact measurements, which are essential in millwright tasks where accuracy is paramount.

Other components, such as the grips, handle, and base, may play roles in the overall function of the micrometer but do not require constant motion during measurement. The grips secure the object being measured, the handle may assist in maneuvering the tool, and the base is usually involved in stabilizing the device during use. However, the thimble's movement is the primary action needed to take measurements effectively.